1. Field of the Invention
The present invention relates to a scanning method for performing a low resolution scan, and more particularly, to a scanning method for performing a low resolution scan by using a high resolution scanning module.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a schematic diagram of the charge coupled device (CCD) 24 of a high resolution scanning module. The main component of the prior art scanning module is a charge coupled device (CCD) 24. The CCD 24 of the prior art high resolution scanning module comprises a plurality of linearly arranged photo sensors 12, a shift register 14, and an output unit 20. The shift register 14 comprises a plurality of serially connected storage units 16 and an output port 18. The number of the storage units 16 is equal to the number of the photo sensors 12 and each of the storage units 16 is electrically connected with one correspondent photo sensor 12. Each photo sensor senses a document and generates the correspondent induced charges, and each storage unit 16 stores the induced charges generated by the connected photo sensor 12. The induced charges stored in the storage units 16 are able to serially migrate toward the output port 18 where they are sequentially output. The output unit 20 is electrically connected to the output port 18 of the shift register 14 and receives the induced charges outputted from the output port 18 to generate a correspondent induced voltage. Therefore, the induced voltage outputted from the output unit 20 possesses image data. The output unit 20 outputs the induced voltage to an A/D converter 22 electrically connected to the output unit 20 where the induced voltage outputted from the output unit 20 is converted into a digital image signal.
When using the CCD 24 of the high resolution scanning module to perform the highest resolution scan on a document, the scanning method comprises the following steps:
Step 1: activating the photo sensors 12 to sense the light transmitted from the document for a predetermined time period to generate correspondent induced charges;
Step 2: transmitting the induced charges from the photo sensors 12 into corresponding storage units 16;
Step 3: shifting the induced charges stored in the storage units 16 into the output unit 20 in sequence;
Step 4: outputting the induced voltage of the output unit 20 after induced charges of one storage unit 16 are accumulated in the output unit 20, and resetting the output unit 20 to continue receiving the induced charges from the output port 18, and using the A/D converter 22 to convert the induced voltage outputted from the output unit 20 into a digital image signal;
Step 5: repeating the previous step until all the induced charges in the storage units 16 are outputted.
Please refer to FIG. 2. FIG. 2 is a schematic diagram of the selection of the image data when performing a low resolution scan according to the prior art. When using the CCD 24 of the high resolution scanning module to perform a low resolution scan, for example, scanning at 600 dpi with the highest possible resolution being 1200 dpi (dots per inch), the difference between the low resolution scan and the high resolution scan is the selection of the image data. As shown in FIG. 2, when scanning is performed at 1200 dpi, the induced charges in each of the storage units 16 are transmitted to the output port 18. When scanning is performed at 600 dpi, the induced charges in every other storage unit 16 are transmitted.
Increases in the speed of transmission of interfaces has led to rapid transmission speeds in current interfaces. The prior art method of discarding part of the image data during low resolution scanning with a high resolution scanning module cannot effectively enhance the scanning speed of the low resolution scan due to exposure time limitations. As a result, the low resolution scan cannot be performed rapidly.
It is therefore a primary objective of the present invention to provide a scanning method for performing a low resolution scan by using a high resolution scanning module to solve the above mentioned problem.
In a preferred embodiment, the present invention provides a scanning method for performing a low resolution scan by using a high resolution scanning module, the scanning module comprising:
a plurality of linearly arranged photo sensors, each of the photo sensors being capable of sensing light transmitted from a document to generate correspondent induced charges;
a shift register comprising a plurality of serially connected storage units and an output port, the number of the storage units being equal to the number of the photo sensors, each of the storage units being electrically connected with one correspondent photo sensor for storing the induced charges generated by the connected photo sensor, the induced charges stored in the storage units being able to serially migrate toward the output port and sequentially output from the output port; and
an output unit electrically connected to the output port of the shift register for receiving the induced charges output from the output port and generating a correspondent induced voltage; the low resolution scanning method comprising:
activating the photo sensors to sense the light transmitted from the document for a first predetermined time period to generate correspondent induced charges;
transmitting the induced charges from the photo sensors into corresponding storage units;
shifting the induced charges stored in the storage units into the output unit in sequence;
outputting the induced voltage of the output unit after induced charges of a first predetermined number of the storage units are accumulated in the output unit, and resetting the output unit to continue receiving the induced charges from the output port; and
repeating the previous step until all the induced charges in the storage units are output.
It is an advantage of the present invention that the exposure time of the photo sensors is shortened when performing a low resolution scan, so the low resolution scan can be performed rapidly.